Tool

ABSTRACT

A tool includes a switch and a controller. The switch is configured to cause an electric component to operate. The switch includes a switch manipulation part and a load sensor. The switch manipulation part is configured to manipulate the switch. The load sensor is configured to detect a load corresponding to a pressing force according to a manipulation of the switch manipulation part. The controller is configured to correct an output corresponding to the load detected by the load sensor. The switch is configured to cause the electric component to operate based on the output corrected by the controller.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. P2015-228223 filed on Nov. 20, 2015.

TECHNICAL FIELD

The present invention relates to a tool.

BACKGROUND

In a general electric tool, a rotational speed of a motor is controlledby a user pulling a trigger provided in a grip. As the trigger, thereare a stroke type trigger which performs a control by an operationamount, a load type trigger which performs a control by a magnitude ofan operation load, and the like. A semiconductor, a strain gauge, or apressure-sensitive conductive elastomer (hereinafter, referred to as apressure-sensitive rubber) is used as a load sensor. For example,JP-A-2007-220481 discloses a pressure-sensitive conductive elastomer inwhich an electric resistance value is high in a non-pressure andnon-deformed state, and the electric resistance value is reducedaccording to the increase of the load at the time of the compressivedeformation so as to show conductivity.

SUMMARY

However, the electric tool adopting the load sensor described inJP-A-2007-220481 and the like has following problems. That is, there isa case where the mechanical strength of the load sensor is changed tocause deterioration (sag). When a temperature becomes high, the hardnessof rubber decreases, and when a temperature becomes low, the hardnessincreases. Therefore, in low temperature environment, the characteristicof a resistance value with respect to a load becomes insensitive, andthe rotational speed of the motor is not increased even when the load isapplied. Such a characteristic of the sensor causes a problem that theoutput with respect to the load corresponding to a pressure operation ofthe user is not stabilized, and operability is degraded.

In this regard, the present invention was made to solve theabove-described problems, and an object thereof is to provide a toolwhich can stabilize output with respect to a load.

According to one aspect of the present invention, a tool includes aswitch and a controller. The switch is configured to cause an electriccomponent to operate. The switch includes a switch manipulation part anda load sensor. The switch manipulation part is configured to manipulatethe switch. The load sensor is configured to detect a load correspondingto a pressing force according to a manipulation of the switchmanipulation part. The controller is configured to correct an outputcorresponding to the load detected by the load sensor. The switch isconfigured to cause the electric component to operate based on theoutput corrected by the controller.

According to the present invention, the stabilized output can beobtained without being affected by a characteristic of a load sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a configuration example of anelectric tool according to an embodiment of the present invention;

FIG. 2 is a sectional view illustrating a configuration example of theelectric tool;

FIG. 3 is a sectional view illustrating a configuration example of aswitch;

FIG. 4 is a sectional view illustrating the configuration example of theswitch;

FIG. 5 is a sectional view illustrating a configuration example of aload sensor;

FIG. 6 is a sectional view illustrating a motion example of the switch;

FIG. 7 is a block diagram illustrating a functional configurationexample of the electric tool;

FIG. 8 is a graph illustrating load-resistance value features before andafter deterioration of the load sensor;

FIG. 9 is a flowchart illustrating a motion example of the electric toolin the case of considering the deterioration of the load sensor; and

FIG. 10 is a flowchart illustrating a motion example of the electrictool in the case of considering temperature variation.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings.

[Configuration Example of Electric Tool 10]

FIG. 1 illustrates an example of a planar configuration of an electrictool 10 according to an embodiment of the present invention. FIG. 2illustrates an example of a sectional configuration thereof. In FIGS. 1and 2, the left side of the drawings is set as the front side of theelectric tool 10, and the right side of the drawings is set as the rearside of the electric tool 10.

The electric tool 10 according to the present invention is an impactdriver having a DC brushless motor (hereinafter, referred to as a motor20) as a driving source. As illustrated in FIGS. 1 and 2, the electrictool 10 includes a cylindrical electric tool body (housing) 12 and agrip 16 extending in a substantially vertical direction from the lowerportion of the electric tool body 12. The side surface portion of theelectric tool body 12 is provided with a normal/reverse switch 60 forswitching the rotation of the motor 20 between positive rotation andreverse rotation.

The motor 20, a cooling fan 22, a reduction gear 40, a spindle 42, ahammer 44, and an anvil 46 are built in the electric tool body 12. Themotor 20 is configured, for example, as a DC brushless motor, and isprovided in the rear portion of the electric tool body 12. The motor 20disclosed in the present invention is an example of an electriccomponent.

The cooling fan 22 is disposed on the rear side of the motor 20, and isprovided coaxially with a rotating shaft 20 a of the motor 20. Thecooling fan 22 rotates according to the rotation of the motor 20. Thecooling fan 22 absorbs external air from an inlet port provided in theside surface portion of the electric tool body 12 to cool the motor 20,and discharges the absorbed air through an exhaust hole provided in theside surface portion of the electric tool body 12.

The reduction gear 40 is provided on the front side of the motor 20 tobe connected to the rotating shaft 20 a of the motor 20. The reductiongear 40 forms a planetary gear mechanism. The reduction gear 40 rotatesaccording to the rotation of the motor 20 and reduces the rotationalspeed of the motor 20 to transmit the power of the motor 20 to thespindle 42.

The hammer 44 converts the rotation of the spindle 42 to the rotarystriking force, and transmits the converted rotary striking force to theanvil 46. Specifically, when an external torque (screw fasteningresistance) of a set torque or more is applied to an output shaft 46 a(to be described later) at the time of the screw fastening motion (atthe time of activation of the motor 20), the hammer 44 retreats whilecompressing a compression spring 45, so that the engagement of the anvil46 and the hammer 44 in a rotation direction is temporarily released.Then, the restoring force of the compression spring 45 causes the hammer44 to advance, and the hammer 44 strikes the anvil 46 in the rotationdirection.

The anvil 46 is provided in the tip portion of the electric tool body12, and includes the output shaft 46 a on which a driver bit (tip tool,not illustrated) is mountable. When the motor 20 is driven to rotate inthe state of attaching the driver bit to the output shaft 46 a, thedriving force of the motor 20 causes the driver bit to rotate and to bestruck.

The grip 16 is a part for gripping the electric tool 10. A battery packattaching part 18 to which a battery 70 can be attached in a mountablemanner is provided in the lower portion of the grip 16. FIGS. 1 and 2illustrate a state where the battery 70 is attached to the battery packattaching part 18. A residual capacity gauge is provided in the battery70 so that battery residual capacity can be recognized visually.

An operation panel 24 is provided in the upper surface portion of theportion which extends to the front side of the battery pack attachingpart 18. The operation panel 24 includes a mode setting button forswitching a strike mode, and the like.

A switch 30 is disposed on the front side of the upper portion of thegrip 16, and is provided in a position where a forefinger is crookedwhen a user grips the grip 16. The rotation amount of the motor 20 canbe controlled according to the pressuring motion (pull operation) of theuser with respect to the switch 30.

[Configuration Example of Switch 30]

FIGS. 3 and 4 illustrate an example of a configuration of the switch 30.As illustrated in FIGS. 3 and 4, the switch 30 includes the trigger 300,a sensor unit 310, a fixing member 350, a temperature sensor(temperature measurement part) 80, and regulating parts 370, 372, and380.

The trigger 300 is a member which is used for the user to turn on/offthe electric tool 10 and to adjust the rotation amount of the motor 20.The trigger 300 is one example of a switch manipulation part. Thetrigger 300 has a curved front surface such that the user easily appliespressure with a finger. A protrusion 300 a protruding toward the sensorunit 310 is provided in the rear surface (back surface) of the trigger300. The protrusion 300 a is moved toward the sensor unit 310 when theuser performs the pressure operation on the trigger 300, and presses aload sensor 320 (to be described later). A coil spring 362 is insertedbetween the trigger 300 and a load sensor covering member 330 (to bedescribed later), and biases the trigger 300 in an opposite direction toa pressing direction R.

The sensor unit 310 includes the load sensor 320, the load sensorcovering member 330, and a load sensor supporting member 340. FIG. 5illustrates an example of the sectional configuration of the load sensor320. As illustrated in FIG. 5, the load sensor 320 includes the sealingcover 322, a pressure-sensitive conductive elastic member 324, and asubstrate 326.

The sealing cover 322 is formed, for example, of soft resin materialwhich can be bent and deformed elastically. The sealing cover 322includes a pressure portion 322 a and a sealing portion 322 b formedintegrally therewith. The pressure portion 322 a has a front surfaceside and a rear surface side, each of which protrudes in a hemisphericalshape (dome shape). The protrusion on the front surface side is advancedand retreated elastically by being pressed by the trigger 300, and theprotrusion on the rear surface side presses the pressure-sensitiveconductive elastic member 324. The pressure portion 322 a is provided tobe separated by a distance D1 from the protrusion 300 a of the trigger300 in order to prevent an erroneous operation (see FIG. 4). The sealingportion 322 b is provided to surround the entire circumference of theouter edge portion of the substrate 326, and has a function to secure awaterproof property in the load sensor 320.

The pressure-sensitive conductive elastic member (movable contact) 324is disposed between the sealing cover 322 and the substrate 326, and isformed of a planar conductive member which can be bent and deformedelastically. As the conductive member, for example, a pressure-sensitiveconductive member in which electric conductivity is changed according topressure may be used in addition to a metallic conductive member. Forexample, a pressure-sensitive member in which conductive fine particlessuch as carbon, metal powders, and metal deposition powders aredispersed to a rubber material may be preferably used. Thepressure-sensitive conductive elastic member 324 abuts on the substrate326 by being bent by a pressing force received from the sealing cover322. In this embodiment, the pressure-sensitive conductive elasticmember (movable contact) 324 and the sealing cover 322 are configured inthe contact state, but may be separated from each other.

The substrate 326 is formed, for example, of a material such as a glassepoxy plate, and is disposed a certain distance D2 away from thepressure-sensitive conductive elastic member 324. A plurality ofconductor patterns (not illustrated) are formed on the front surfaceside of the substrate 326 to form fixed contacts. When thepressure-sensitive conductive elastic member 324 is compressed in thestate of abutting on the conductor patterns, a resistance value ischanged according to a compression load (deformation amount) so that thesubstrate 326 becomes conductive. An electric signal based on theconduction is output to a control device 50 (to be described later)through a wire 360 connected to the substrate 326. When the deformationamount of the pressure-sensitive conductive elastic member 324 isincreased by the increase of the load, the resistance value isdecreased. In this manner, it is possible to detect the resistance valuewith respect to the load corresponding to the pressing force of the userto the trigger 300.

Returning to FIGS. 3 and 4, the load sensor covering member 330 securesa sealing property and a waterproof property of the load sensor 320 bycovering the load sensor 320. The load sensor covering member 330includes a cylindrical portion 332, and a flange portion 334 formedintegrally therewith. In the cylindrical portion 332, the pressureportion 322 a is exposed so that the protrusion 300 a can press thepressure portion 322 a. The flange portion 334 is provided to extendoutward from the outer edge of the cylindrical portion 332, and to coverthe entire circumstance of the outer edge portion of the sealing cover322.

The load sensor supporting member 340 is a member for supporting theload sensor 320, and includes a cylindrical portion 342 and a flangeportion 344 formed integrally therewith. The cylindrical portion 342 isa cylindrical member including a step portion, and includes a largediameter cylindrical portion 342 a and a small diameter cylindricalportion 342 b connected thereto. The flange portion 344 extends from thefront outer edge of the large diameter cylindrical portion 342 a, andabuts on each of the flange portion 334 of the load sensor coveringmember 330 and the sealing portion 322 b of the sealing cover 322 (seeFIG. 5).

The flange portion 334 of the load sensor covering member 330 and theflange portion 344 of the load sensor supporting member 340 are fastenedby screws 366 and 368 in a state where the sealing portion 322 b of thesealing cover 322 is interposed therebetween. In this manner, the loadsensor 320 is configured as an integral unit structure contained in theload sensor covering member 330 and the load sensor supporting member340 (sensor unit 310), thereby securing the sealing property and thewaterproof property of the load sensor 320.

The fixing member 350 is fixed to an attachment portion (notillustrated) provided in the electric tool body 12, and regulates themovement of the trigger 300 and the sensor unit 310 in the pressingdirection R. The fixing member 350 includes a guide part 350 a forguiding the movement of the sensor unit 310. The guide part 350 a isprovided in the inner circumferential surface of the fixing member 350,and contacts the outer circumferential surface of the cylindricalportion 342 so that the sensor unit 310 can move linearly in thepressing direction R. A spring 364 is inserted between the outercircumferential surface of the small diameter cylindrical portion 342 bof the load sensor supporting member 340 and the inner circumferentialsurface of the fixing member 350. The sensor unit 310 is supportedelastically by the coil spring 364.

The coil spring 364 is disposed coaxially with the load sensor 320, andis elastically deformed when a certain load or more is applied to theload sensor 320 by pressure of the user with respect to the trigger 300.In this manner, the sensor unit 310 can be configured to be movable tothe fixing member 350, and the pressing force received by the trigger300 can be accurately transmitted to the load sensor 320. Therefore, itis possible to improve the sensitivity of the load sensor 320. The coilspring 364 disclosed in the present invention is an example of anelastic member.

The temperature sensor 80 is configured, for example, as a thermistor,and is provided in the rear surface (back surface) side of the substrate326 forming the load sensor 320. The temperature sensor 80 may measurean ambient temperature in a state where the electric tool 10 is usedafter turning on a power supply as well as the temperature of the loadsensor 320. The ambient temperature includes, for example, an ambienttemperature of the load sensor 320 in the electric tool body 12, and anenvironmental temperature near the electric tool body 12. In this case,it is preferable to change a place to attach the temperature sensor 80appropriately.

As illustrated in FIG. 4, the regulating parts 370 and 372 are providedin the respective upper portion and lower portion of the inside of theswitch 30, and regulate the movement distance of the trigger 300according to the pressure of the user to be less than the maximummovement distance of the sensor unit 310.

The regulating part 370 includes a protrusion 302 provided in thetrigger 300 and a long hole 352 which is provided in the fixing member350 and extends in the pressing direction R of the trigger 300. Theprotrusion 302 is a columnar member protruding from the inner surface ofthe trigger 300 toward the fixing member 350, and is engaged to beslidable in the long hole 352. A movement distance (stroke) D3 of theprotrusion 302 of the trigger 300 in the long hole 352 is less than themaximum movement distance (stroke) of the sensor unit 310 in thepressing direction R.

The regulating part 372 will be not described in detail because theregulating part 372 has the same configuration as the regulating part370. The regulating part 372 includes a protrusion 304 and a long hole354. The protrusion 304 is engaged to be slidable in the long hole 354.A movement distance D4 of the protrusion 304 of the trigger 300 in thelong hole 354 is less than the maximum movement distance of the sensorunit 310 in the pressing direction. The movement distance D3 is the sameas the movement distance D4.

The regulating part 380 is provided in the rear portion of the switch30. The regulating part 380 prevents the sensor unit 310 from coming offfrom the coil spring 364, and regulates the movement amount of thesensor unit 310. The regulating part 380 includes a protrusion 356provided in the fixing member 350, and a hook portion 342 c provided inthe load sensor supporting member 340.

The hook portion 342 c includes a recess concave downward, and is formedintegrally with the rear end portion of the load sensor supportingmember 340. The protrusion 356 is a columnar member which protrudes fromthe inner surface of the fixing member 350 toward the load sensorsupporting member 340, and is engaged to the hook portion 342 c in amovable manner. A movement distance D5 of the protrusion 356 in the hookportion 342 c is set to such a length that the sensor unit 310 ismovable even when the stroke of the trigger 300 reaches a limit.

[Motion Example of Switch 30]

Next, a motion example of the switch 30 will be described with referenceto FIGS. 3 and 6. FIG. 6 illustrates an example of a motion of pullingthe switch 30. In a state before the trigger 300 is pressed by the user,the trigger 300 and the sealing cover 322 are separated by the distanceD1 from each other, and the pressure-sensitive conductive elastic member324 and the substrate 326 are separated by the distance D2 from eachother. In this case, the load sensor 320 is in a non-conductive state.Before the trigger 300 is pressed, the coil spring 364 biases the sensorunit 310 toward the trigger 300, but the hook portion 342 c is locked bythe protrusion 356. In this manner, it is possible to prevent the sensorunit 310 from coming off from the fixing member 350.

When the user performs the pressure operation on the trigger 300, thetrigger 300 moves in the pressing direction R, and the protrusion 300 aof the trigger 300 abuts on the pressure portion 322 a of the sealingcover 322 and presses the pressure portion 322 a. When the trigger 300is further pressed, the pressure portion 322 a of the sealing cover 322presses the pressure-sensitive conductive elastic member 324. In thismanner, the pressure-sensitive conductive elastic member 324 iselastically deformed and bent to contact the substrate 326. That is, thetrigger 300 (protrusions 302 and 304) moves by the displacement amountallowed in the distances D1 and D2 in the pressing direction R.

As illustrated in FIG. 6, when the user further performs the pressureoperation on the trigger 300, and a load equal to or more than theattachment load of the coil spring 364 is applied to the trigger 300,the coil spring 364 is compressed, and the sensor unit 310 containingthe load sensor 320 moves in the pressing direction R (rearward). Whenthe sensor unit 310 moves by the distance D3, the movement of thetrigger 300 including the protrusions 302 and 304 is regulated by thelong holes 352 and 354. That is, the trigger 300 reaches a stroke limitbefore the sensor unit 310 reaches a stroke limit. In this manner, it ispossible to prevent a load equal to or more than that of the coil spring364 from being applied to the load sensor 320.

Even in a case where the trigger 300 moves by the maximum distance whichis regulated by the regulating parts 370 and 372, the protrusion 356 inthe hook portion 342 c is in the state of being movable by a distanceD6. That is, the sensor unit 310 is configured to be movable with amargin of the distance D6 to the fixing member 350. In this manner, itis possible to prevent the damage and the like of the load sensor 320even in a case where an excessive load is applied to the load sensor320.

[Block Configuration Example of Electric Tool 10]

FIG. 7 is a block diagram illustrating an example of a functionalconfiguration of the electric tool 10. As illustrated in FIG. 7, theelectric tool 10 includes the control device 50 (controller) forcontrolling the entire motion of the electric tool 10. The controldevice 50 is a microcomputer which mainly includes a CPU (CentralProcessing Unit) 52, a ROM (Read Only Memory) 54, and a RAM (RandomAccess Memory) 56. The control device 50 executes a correction motion ofcorrecting an error, which is generated by the deterioration of theswitch 30 and the like, a control of driving the motor 20, and the likeaccording to a program stored in advance in the ROM 54 and the like.

The control device 50 is connected with the load sensor 320, thetemperature sensor 80, the normal/reverse switch 60, the motor 20, alighting device 62, the operation panel 24, the battery 70, and astorage unit 90.

The load sensor 320 detects a load corresponding to a pressing force ofthe user with respect to the trigger 300, and supplies a detectionsignal based on the detection to the control device 50. The temperaturesensor 80 detects a temperature (ambient temperature) of the load sensor320, and supplies temperature information to the control device 50. Thenormal/reverse switch 60 supplies a switch signal based on a positiverotation/reverse rotation switch operation of the user with respect tothe control device 50.

The motor 20 is driven to rotate based on a driving signal supplied fromthe control device 50. The lighting device 62 is formed, for example, ofa plurality of LEDs provided in the electric tool body 12, and islighted on or is lighted off based on the driving signal supplied fromthe control device 50. The operation panel 24 switches a display basedon the instruction of the control device 50.

The battery 70 supplies power to the components such as the controldevice 50. The storage unit 90 is formed, for example, of a nonvolatilesemiconductor memory, and stores a load-resistance value featureindicating a load and a resistance value as a reference value, and atable storing a plurality of load-resistance value features indicatingthe load and the resistance value set at each temperature. For example,the load-resistance value feature can be set at each of −10° C., 0° C.,25° C., 30° C., and 40° C. as a temperature. The load-resistance valuefeature may be set as a function formula in advance, so that aresistance value with respect to a load is computed through real timecomputation.

[Load-Resistance Value Feature]

The load sensor 320 has a problem that the output feature with respectto a load is changed due to the deterioration or the temperaturevariation. FIG. 8 is a graph illustrating an example of a relationbetween a load detected by the load sensor 320 and a resistance value.In FIG. 8, a solid line indicates a load-resistance value feature(reference value) before the deterioration of the load sensor 320, and abroken line indicates a load-resistance value feature after thedeterioration of the load sensor 320. The axis of ordinates indicatesthe resistance value, and the axis of abscissas indicates the load.

As illustrated in FIG. 8, in the load-resistance value feature beforethe deterioration, when a load detected by the load sensor 320 islarger, a resistance value with respect to the load becomes smaller. Onthe other hand, in the load-resistance value feature after thedeterioration, when the load detected by the load sensor 320 is larger,the resistance value becomes smaller. However, the resistance value withrespect to the load is declined more insensitively compared with thecase before the deterioration, and the resistance value is larger thanthe case before the deterioration. As a result, a rotational speed ofthe motor 20 is increased by a small load, and thus there is a problemthat it is not possible to obtain the accurate rotational speed of themotor 20 corresponding to the load.

In this regard, in this embodiment, a correction on the output errorgenerated by the deterioration of the load sensor 320 and the like isperformed in such a manner that the resistance value with respect to acertain load is detected, the difference between the detected resistancevalue and the reference value is set as a correction value, and then thecorrection value is reflected on the resistance value with respect tothe load detected by the load sensor 320. Herein, the certain load inthis embodiment indicates a maximum load obtained through the coilspring 364 as a load adjusting mechanism.

For example, as illustrated in FIG. 8, in a case where the certain loadis set to 1000 (gf), it is obtained a resistance value R1 in a casewhere the load detected by the load sensor 320 reaches approximately1000 (gf). Continuously, a difference C between a resistance value R2 asa reference value in the case of a load of 1000 (g) and the obtainedresistance value R1 is calculated. The difference C is set as acorrection value for correcting the output difference generated due tothe deterioration and the like. The load-resistance value feature beforethe deterioration and the load-resistance value feature after thedeterioration are deviated by the almost same deviation amount, and thusthe same correction value can be also used to a resistance value withrespect to another load. Of course, the calculated correction value maybe further corrected in each detected load. The certain load may be setarbitrarily with the adopted coil spring 364 and the like, and is notlimited to the above-described 1000 (gf).

Herein, the determination on whether the load applied to the load sensor320 reaches the certain load can be performed as follows. When apredetermined load or more is applied, the electric tool 10 performs ascrew fastening by the hammer 44 applying a rotational strike to theanvil 16. Since the impact generated by the strike is transmitted alsoto the load sensor 320, the signal of the load detected by the loadsensor 320 is periodically varied. At this time, the load sensor 320becomes more stable when the trigger 300 is grasped more strongly.Accordingly, when the trigger 300 is grasped strongly, the variation(amplitude) of the resistance value detected by the load sensor 320becomes small, and when the trigger 300 is grasped weakly, the variation(amplitude) of the resistance value becomes large. In this regard, inthis embodiment, in consideration with the change of the amplitude ofthe resistance value according to a force of holding the trigger 300, ina case where the amplitude of the resistance value is equal to or lessthan a preset threshold value, it is determined that the load applied tothe load sensor 320 reaches a certain load (maximum load).

[Motion Example (First) of Electric Tool 10]

FIG. 9 is a flowchart illustrating an example of a correction motion ofthe electric tool 10 in the case of considering the deterioration of theload sensor 320. The correction motion (to be described later) of theelectric tool 10 is performed when the control device 50 (CPU 52)executes the program stored in the ROM 54.

As illustrated in FIG. 9, in Step S100, the control device 50 determineswhether the user operates the trigger 300. In a case where it isdetermined that the user does not operate the trigger 300, the controldevice 50 stands by until the user operates the trigger 300. On theother hand, in a case where it is determined that the user operates thetrigger 300, the control device 50 progresses to Step S110.

In Step S110, the load sensor 320 detects the load corresponding to thepressing force of the user with respect to the trigger 300. The controldevice 50 calculates the resistance value with respect to the loaddetected by the load sensor 320. After Step S110 is ended, the procedureproceeds to Step S120.

In Step S120, the control device 50 determines whether the amplitude ofthe calculated resistance value is equal to or less than the presetthreshold value. That is, it is determined whether the load detected bythe load sensor 320 reaches a certain load (maximum load). In a casewhere the amplitude of the obtained resistance value is not equal to orless than the threshold value, that is, a case where the amplitude ofthe resistance value exceeds the threshold value, the control device 50determines that the load does not reach a certain value, and progressesto Step S110. The control device 50 continuously monitors the amplitudeof the resistance value. On the other hand, in a case where it isdetermined that the amplitude of the obtained resistance value is equalto or less than the threshold value, the control device 50 progresses toStep S130.

In Step S130, the control device 50 obtains the resistance value in acase where the load reaches the certain value. That is, it is obtainedthe resistance value in a case where the maximum load is applied to theload sensor 320 by the pressure operation of the user with respect tothe trigger 300. After Step S130 is ended, the procedure proceeds toStep S140.

In Step S140, the control device 50 reads the preset reference value(load-resistance value feature) from the storage unit 90, and calculatesthe correction value based on the comparison result between the readreference value and the obtained resistance value. The reference valueis a normal resistance value of the load sensor 320 obtained, forexample, before the deterioration occurs in the load sensor 320 (beforehandling). After Step S140 is ended, the procedure proceeds to StepS150.

In Step S150, the control device 50 corrects the resistance value(output), which is detected by the load sensor 320, corresponding to thepressure of the user with respect to the trigger 300 by using thecalculated correction value. The control device 50 can perform therotation driving on the motor 20 without being affected by thedeterioration of the load sensor 320 by outputting a voltage signalbased on the corrected resistance value to the motor 20.

[Motion Example (Second) of Electric Tool 10]

FIG. 10 is a flowchart illustrating an example of the correction motionof the electric tool 10 in the case of considering the temperaturevariation of the load sensor 320. This correction motion may bepreferably applied to, for example, a case where the load of the loadsensor 230 does not reach a certain load, and after the operation isperformed in a place with a high temperature, and then the operation isperformed after moving to a place with a low temperature. For example,the correction motion may be preferably applied also to a case where ina season with an extreme temperature difference, the operation isperformed at day, and then the operation is performed at night.

The correction motion (to be described later) of the electric tool 10 isperformed when the control device 50 (CPU 52) executes the programstored in the ROM 54. Specifically, in Step S200, the control device 50determines whether the user operates the trigger 300. In a case where itis determined that the user does not operate the trigger 300, thecontrol device 50 continuously monitors whether the user performs theoperation. On the other hand, in a case where it is determined that theuser operates the trigger 300, the control device 50 progresses to StepS210.

In Step S210, according to activation of the control device 50, thetemperature sensor 80 measures the temperature of the load sensor 320.After Step S210 is ended, the procedure proceeds to Step S220.

In Step S220, the control device 50 selects a load-resistance valuefeature (reference value), which is a reference corresponding to thetemperature of the load sensor 320 measured by the temperature sensor80, among a plurality of load-resistance value features stored withrespect to respective temperatures, and reads the load-resistance valuefeature. After Step S220 is ended, the procedure proceeds to Step S230.

In Step S230, the control device 50 obtains a load corresponding to thepressing force of the user with respect to the trigger 300 from the loadsensor 320, and calculates a resistance value with respect to theobtained load. The examples thereof include a case where the trigger 300starts the first movement, and a case where the trigger 300 is pulled inthe state of not fastening the screw. After Step S230 is ended, theprocedure proceeds to Step S240.

In Step S240, the control device 50 obtains a resistance value, which isa reference corresponding to a load matching the load corresponding tothe pressing force of the user, based on the load-resistance valuefeature read from the storage unit 90. After Step S240 is ended, theprocedure proceeds to Step S250.

In Step S250, the control device 50 calculates the correction value bycomparing between the resistance value with respect to the loadcorresponding to the pressing force of the user and the reference valueof the resistance value obtained from the load-resistance value feature.After Step S250 is ended, the procedure proceeds to Step S260. Acomparison between an output value of the load sensor 320 and thereference value may be performed, and in a case where the output isseparated largely from the reference value, it may be determined andnotified that the output is abnormal. As a notification means, forexample, voice or a buzzer may be adopted, and a lighting display usingLED and the like may be adopted. In this manner, it is possible to checkwhether abnormality occurs in the electric tool 10.

In Step S260, the control device 50 corrects the resistance value, whichis detected by the load sensor 320, corresponding to the pressure of theuser with respect to the trigger 300 by using the calculated correctionvalue. The control device 50 can perform the rotation driving on themotor 20 without being affected by the temperature variation byoutputting a voltage signal based on the corrected resistance value tothe motor 20.

As illustrated above, in this embodiment, the output correction isperformed based on the difference between the resistance value withrespect to the detected load, and the reference value. Therefore, it ispossible to obtain a stabilized operation feeling of the switch 30without being affected by the deterioration of the load sensor 320 orthe temperature variation in the use environment. For example, in therelated art, in the case of using the rubber load sensor 320, thehardness of the rubber may be changed by the temperature variation, andthe desired rotation of the motor 20 may be not obtained. However, inthis embodiment, the load-resistance value feature as a reference isstored at each environmental temperature, and the correctioncorresponding to the temperature is performed, so that it is possible toperform a highly precise operation regardless of the temperaturevariation.

In this embodiment, for example, at the time of starting to use theelectric tool 10, the correction motion illustrated in FIG. 10 can beperformed, and after starting to use the electric tool 10, thecorrection motion illustrated in FIG. 9 can be performed. In thismanner, even in a case where the load sensor 320 does not reach acertain load similarly with the time of starting to use the electrictool 10, it is possible to accurately correct the resistance value withrespect to the load. In the correction motions illustrated in FIGS. 9and 10, only one correction motion thereof may be embedded to theelectric tool 10, and both the correction motions may be embedded to theelectric tool 10.

The technical range of the present invention is not limited to theabove-described embodiments, and the above-described embodiments may bemodified in various forms without departing from the scope of thepresent invention. The description has been given about an example thatthe rubber load sensor of the pressure-sensitive type is used as anexample of the load sensor 320. Additionally, the present invention maybe applied also to the case of using a semiconductor-type load sensor,or a strain gauge-type load sensor.

In the above-described embodiment, in a case where the output correctionis performed in consideration of the temperature variation, theload-resistance value feature and the function formula are stored ateach temperature. However, the invention is not limited thereto. Forexample, a plurality of load-resistance value features (output feature)or function formulas may be stored in correspondence with the preferenceof the user. Specifically, it is considered that the correction motionsare performed which correspond to a user who desires to obtain a strongoutput with a light pull operation, a user who desires to obtain,adversely, a corresponding output with a heavy pull operation, and thelike.

When an operation is performed finely, the correction may be performedto be sensitive to the sensitivity of the trigger 300 even during normaltime, thereby improving the response of the electric tool 10.

Without depending on a pulling method of the trigger 300, theload-output feature may be changed according to load areas by performinga correction, which allows the driving of starting a rotation slowly atthe beginning of pulling and making the rotation gradually faster, and acorrection of making the rotation reach a maximum speed rapidly. Inorder that a proper use in correspondence with an operation target canbe easily performed, it is considered that a correction of setting theupper limit of the output (rotational speed) is performed to obtain apredetermined output without depending on a pulling method of thetrigger 300. At this time, it may be configured that the feature incorrespondence with the preference of the user is selectable from aplurality of output features which are stored in advance. When it is setto store an arbitrary load, it is possible to improve usability.

In the above-described embodiment, the output at the time of the certainload is corrected, but the invention is not limited thereto. Forexample, when it is satisfied at least one condition of the presetoperating time of the electric tool 10 and the preset number of times ofthe operation, the output with respect to the load detected by the loadsensor 320 may be corrected. In this case, the correction value ispreferably set in proportion to the operating time and the number oftimes of the operation.

In the regulating parts 370 and 372 of the above-described embodiment,the relation between the protrusions 302 and 304 and the long holes 352and 354 may be configured adversely. Similarly, the protrusion 356 andthe hook portion 342 c of the regulating part 380 may be configuredadversely. The method of determining whether the load applied to theload sensor 320 reaches a certain load is not limited to theabove-described embodiment. A displacement sensor may be used to detectthe maximum amount of the stroke of the trigger 300.

(1) A tool comprising:

a switch that is configured to cause an electric component to operate;and

a controller,

wherein the switch includes:

-   -   a switch manipulation part that is configured to manipulate the        switch; and    -   a load sensor that is configured to detect a load corresponding        to a pressing force according to a manipulation of the switch        manipulation part, and

wherein the controller is configured to correct an output correspondingto the load detected by the load sensor, and

wherein the switch is configured to cause the electric component tooperate based on the output corrected by the controller.

(2) The tool according to (1), wherein

the controller is configured to correct the output of the load sensorbased on comparison between the output of the load sensor in apredetermined load and a reference value.

(3) The tool according to (2), wherein

the controller is configured to correct the output of the load sensorbased on a load in a case where an output waveform amplitude of the loadsensor in the predetermined load is a threshold value or less than thethreshold value.

(4) The tool according to (2) or (3), further comprising:

a load adjusting mechanism that is configured to apply the predeterminedload to the load sensor.

(5) The tool according to (4), wherein

the load adjusting mechanism includes an elastic member which iselastically deformed when a prescribed load or more is applied to theload sensor, and

the load adjusting mechanism is configured to be movable in a directionof the load applied by a pressure operation.

(6) The tool according to any one of (1) to (5), further comprising:

a temperature measurement part, wherein

the controller is configured to correct the output corresponding to theload detected by the load sensor based on a temperature of the loadsensor measured by the temperature measurement part, or based on anambient temperature measured by the temperature measurement part.

(7) The tool according to (6), wherein

the temperature measurement part is provided inside a sensor housingmember in which the load sensor is housed.

(8) The tool according to any one of (1) to (7), wherein

the controller is configured to select a specific reference value from aplurality of reference values, and is configured to correct the outputof the load sensor based on the selected reference value.

(9) The tool according to any one of (1) to (8), wherein

the load sensor includes:

-   -   a pressure-sensitive conductive elastic member in which        conductive particles are dispersed in a switch manipulation        material, and    -   a substrate which is configured to conduct current by the        pressure-sensitive conductive elastic member.        (10) The tool according to (1), wherein

the controller is configured to correct the output of the load sensorbased on at least one of operating time of the tool and the number oftimes of manipulations.

What is claimed is:
 1. A tool comprising: a switch that is configured tocause an electric component to operate; and a controller, wherein theswitch includes: a switch manipulation part that is configured tomanipulate the switch; and a load sensor that is configured to detect aload corresponding to a pressing force according to a manipulation ofthe switch manipulation part, and wherein the controller is configuredto correct an output corresponding to the load detected by the loadsensor, and wherein the switch is configured to cause the electriccomponent to operate based on the output corrected by the controller. 2.The tool according to claim 1, wherein the controller is configured tocorrect the output of the load sensor based on comparison between theoutput of the load sensor in a predetermined load and a reference value.3. The tool according to claim 2, wherein the controller is configuredto correct the output of the load sensor based on a load in a case wherean output waveform amplitude of the load sensor in the predeterminedload is a threshold value or less than the threshold value.
 4. The toolaccording to claim 2, further comprising: a load adjusting mechanismthat is configured to apply the predetermined load to the load sensor.5. The tool according to claim 4, wherein the load adjusting mechanismincludes an elastic member which is elastically deformed when aprescribed load or more is applied to the load sensor, and the loadadjusting mechanism is configured to be movable in a direction of theload applied by a pressure operation.
 6. The tool according to claim 1,further comprising: a temperature measurement part, wherein thecontroller is configured to correct the output corresponding to the loaddetected by the load sensor based on a temperature of the load sensormeasured by the temperature measurement part, or based on an ambienttemperature measured by the temperature measurement part.
 7. The toolaccording to claim 6, wherein the temperature measurement part isprovided inside a sensor housing member in which the load sensor ishoused.
 8. The tool according to claim 1, wherein the controller isconfigured to select a specific reference value from a plurality ofreference values, and is configured to correct the output of the loadsensor based on the selected reference value.
 9. The tool according toclaim 1, wherein the load sensor includes: a pressure-sensitiveconductive elastic member in which conductive particles are dispersed ina switch manipulation material, and a substrate which is configured toconduct current by the pressure-sensitive conductive elastic member. 10.The tool according to claim 1, wherein the controller is configured tocorrect the output of the load sensor based on at least one of operatingtime of the tool and the number of times of manipulations.